The subject matter disclosed herein relates to a steam turbine nozzle assembly, or diaphragm stage. Specifically, the subject matter disclosed herein relates to a casing support block for a steam turbine nozzle assembly.
Steam turbines include static nozzle assemblies that direct flow of a working fluid into turbine buckets connected to a rotating rotor. The nozzle construction (including a plurality of nozzles, or “airfoils”) is sometimes referred to as a “diaphragm” or “nozzle assembly stage.” Steam turbine diaphragms include two halves, which are assembled around the rotor, creating horizontal joints between these two halves. Each turbine diaphragm stage is vertically supported by support bars, support lugs or support screws on each side of the diaphragm at the respective horizontal joints. The horizontal joints of the diaphragm also correspond to horizontal joints of the turbine casing, which surrounds the steam turbine diaphragm.
Support bars are typically attached horizontally to the bottom half of the diaphragm stage near the horizontal joints by bolts. The typical support bar includes a tongue portion that fits into a pocket which is machined into the diaphragm. This support bar also includes an elongated portion which sits on a ledge of the turbine casing. Performing diaphragm maintenance may require accessing the bottom half of the diaphragm, which is incapable of rotating about the turbine rotor due to the support bars and a centering pin coupling the bottom half of diaphragm to the casing. Additionally, removal of the bottom half of the diaphragm may also be necessary in order to align the bottom half with the horizontal joint of the casing. In order to access the bottom half of the diaphragm, a number of time-consuming and costly steps could be undertaken.